<!DOCTYPE html>
<meta charset="utf-8">
<style>
    .ref { background-color: oklch(0 0.2 45); border: 1px solid black; width: 200px; height: 200px; }
</style>
<body>
    <p>Test passes if you see a square border with a single color inside.</p>
    <div class="ref"></div>
</body>
